Heretofoŕe, ball bearings have been employed in an ABS system of automobile. This is because bearings of an automobile ABS system are subjected to a high load. If sintered bearings can be employed instead of expensive ball bearings, then the ABS system would be able to be made up at a lower cost. However, because the load applied to the bearings of an ABS system of automobile sometimes exceeds an allowable load range of a conventional sintered bearing, it has been difficult to employ the conventional sintered bearing.
Further, Fe—Cu-based sintered bearings have been employed for bearings of a wiper motor system of automobile. This is because the wiper motor system in automobile has become increasingly smaller and thus the bearings employed therein have been reduced in size, thus leading to the increase in load applied to the bearing of the wiper motor system. Whilst Fe—Cu-based bearings excel in strength and hardness as compared to Cu-based sintered bearings; they may cause abnormal abrasion and seizure due to the same-metal phenomenon when a Fe-based material is used for a shaft borne by the bearing, thus leading to the problem that the reliability thereof as a sliding member is insufficient.
On the other hand, Japanese unexamined patent application publication No. H05-195117 discloses a Cu-based sintered alloy that is employed as a sliding member such as a valve guide or the like used for internal combustion engine and has excellent abrasion and seizure resistances under high temperature, high load and poor lubrication conditions. Problem to be solved by the invention
The Cu-based sintered alloy disclosed in Japanese unexamined patent application publication No. H05-195117 is one where abrasion and seizure resistance are imparted thereto by adding Ni-based hard particles having favorable adhesion to a matrix and MoS2 as a solid lubricant, to a Cu—Ni—Sn-based alloy having such a composition that allows hardening to be caused by spinodal decomposition. However, since the expensive Ni-based hard particles are used to produce the Cu-based sintered alloy, there has been such a cost problem that it is unable to be produced at low cost. Besides, since the Ni-based hard particles used for the Cu-based sintered alloy contain Cr, adhesion to the matrix is not necessarily sufficient in performing an atmospheric sintering inside a continuous furnace that excels in mass productivity when performing a sintering process. Therefore, there has been a production problem that there could not be stably obtained products excellent in both abrasion and seizure resistances.